Intelligence on Earth Evolved Independently at Least Twice

A series of studies published in Science in February 2025 provides the best evidence yet that birds and mammals did not inherit the neural pathways that generate intelligence from a common ancestor, but rather evolved them independently.

This suggests that vertebrate intelligence arose not once, but multiple times.

The findings could teach us something about how complex circuits in our own brains evolved.

Harvey Karten , a neuroanatomist at the Massachusetts Institute of Technology , mapped and compared brain circuits in mammals and pigeons in the 1960s .

He found that in the bird brain, the dorsal ventricular ridge ( DVR ) seemed to be comparable to a neocortex; it just didn’t look like it.

A few decades later , Luis Puelles , an anatomist in Spain , drew the opposite conclusion.

Studies provide the clearest evidence yet that birds and mammals independently evolved brain regions for complex cognition.

They echo previous research from Tosches ’ lab, which found that the mammalian neocortex evolved independently from the reptile DVR .

The findings haven’t completely resolved Karten and Puelles’ debate, however.